Neuroimmune alterations of ENS functioning

Only recently has it been considered that numerous interactions between the enteric nervous system and local immunocytes are responsible for adaptive functional changes, including motility and secretion (fig 1). Several neuropeptides such as tachykinins, vasoactive intestinal peptide, somatostatin, and opioids are involved in both intrinsic and extrinsic innervation but can also affect immune reactions directly. They exert a dual role in the regulation of local and peripheral motor and secretory reflexes and affect the release of cytokines and proinflammatory mediators. On the other hand, proinflammatory mediators such as eicosanoids and cytokines may activate intrinsic neurones directly or stimulate extrinsic neurones indirectly, releasing neuropeptides which act on intrinsic neurones, smooth muscle cells, or enterocytes. These acute immediate neuroimmune reactions are often followed by long term changes in the number of receptors at the presynaptic or postsynaptic level as well as phenotypic changes of the effector cells, as evidenced for smooth muscle cells and enteric neurones which can synthetise cytokines. Figure 1 Interaction between the central nervous system and the immune system. VIP, vasoactive intestinal peptide; SP, substance P; SOM, somatostatin; G, ganglion; GALT, gut associated lymphoid tissue; MLN, mesenteric lymph node. (From Ottaway.20) There are at least three major target cells affected by the presence of inflammatory mediators: smooth muscle cells, glial cells, and neurones. Both intrinsic enteric neurones and terminals of extrinsic afferent and efferent nerves are affected …